Resonators may be a passive component that is used as a channel filter in radio transmission links (or radio transmission paths). Typically, channel filters used in practice are comprised of multiple resonators that are coupled with each other. With an increasing frequency of the signal transmission of a radio link (radio path), the requirements of the filters vary or change. In particular, the requirements may relate to structural and spatial requirements as well as to requirements with regard to the effectively usable bandwidth of a filter. The effectively usable bandwidth is that frequency bandwidth for which a filter behavior about a central frequency is constant or almost constant.
Depending on the resonance frequency of a filter, it is typically required to adapt the geometric dimensions of a filter, for example.
Typically, channel filters are used to filter the desired signal from a broad frequency spectrum. These channel filters typically have a fix center frequency and a fix bandwidth. However, as a certain flexibility of the bandwidth is often requested, it is desirable to have adjustable resonators.
EP 2 991 158 A1 and US 2016/0064790 A1 describe a channel filter with an adjusting element designed as an adjusting disk. Thereby, adjusting the resonance frequency is enabled throughout a large range and in small steps. However, apart from highly precise actuators, a corresponding control is required for adjusting. In particular for aerospace applications, this may be very expensive.
For example, channel filters may be utilized in so called output multiplexers. A typical output multiplexer is comprised of channel filters that are connected to a waveguide busbar system. A function of the output multiplexer is to combine small-band communication signals onto a common waveguide (the so-called busbar system). Typically, the channel filters and the busbar are adjusted to each other in a costly design process. Furthermore, the individual components for the channel filters as well as the busbar and possibly required additional components can be ordered and manufactured only after finishing this design process.